Electric-furnace process.



G. 0. SEWARD & F. VON KITGELGEN.

ELECTRIC FURNAGE PROCESS.

APPLICATION FILED FEB. 21, 1906.

898,691. Patented Sept. 15,190&

kaigli i iii.

INVENTORS; WITNESSES: g

UNITED STATES PATENT OFFICE.

GEORflE O. SEWARI) AND FRANZ VON KUGIELGEN, ()l IIOLOOMBS ROCK, VIRGINIA, ASSIGNORS, BY MESNE ASSIGNMENT TO ELECIRO META LLUItGlUAlJ (10M PAN Y, A CORPORATION OF WEST VIRGINIA.

Specification of Letters Patent.

ELECTRIC-FURNACE PROCESS.

Patented Sept. 15, 1908.

To all whom it may concern:

Be it known that we, Gnome O. SEWARD, a citizen of the United States, and FRANZ VON KiioELonN, a subject of the German Emperor, both residin rat llolcombs Rock, in the county of Bcdfor and State of Virginia have jointly invented certain new and useful Improvements in Electric-Furnace Processes of which the following is a specification.

This invention relates to a process of performing electric smelting or other smelting operations by means of an electric furnace.

In the production of that class of metals of which ferro-chrome may be considered representative, it is customary to feed a charge consisting of a more or less intimate mixture of the ore, carbon, and a flux into an electric furnace, feedin the charge at such a rate that only a shallow layer of unfused mixture floats upon the molten bath. In such mode of operation much heat is lost b radiation from the zone of reduction throu ii the charge, while the electrode is insu' lciently rotected from oxidation by the air above t 6 charge, and becomes reduced in size before entering the charge.- The elliciency of the furnace is small, and regularity of operation is d-iilicult.

It has often been proposed to keep such a deep layer of the mixture above the zone of reduction that the heat is kept in, and the ascending gases preheat to some extent the descending charge, but the extent to which this has been accomplished hitherto is inconsiderabla. It hasnot been found practical to'maintain a deep layer of mixture above,

the molten bath on account of the extreme difiiculty of regaining the are after re lacing a used-up electrode with a new one, t e mixture invariably fallin into the cavity left by the withdrawal of t e -old pencil from the furnace and closing it. Particularly is it difficult if the layer of mixture is very deep as it should be to get the best eiliciency and to protect the pencil from oxidation above the charge. It has been proposed to nearly empty the furnace or reduce the level of the mixture preliminary to changing a pencil, but there are obvious practical. reasons for not ado ting such procedure.

The 0 ject of the present invention is to enable the production of ferro-chromium and similar alloys to be effected by acontinuous process in which the furnace is kept full of mixture to such a depth thatthe heat losses are a minimum and the pencils are cool where they emerge from the mixture, and, therefore, are not burned b the air.

Our invention provides or renewing the electrode in such a way that there is formed no cavity in the charge, thus avoiding entirely the dilliculty in regaining the are which has hitherto prevailed. We accomplish this by leaving the electrode buried in the mixture, removing the holder therefrom when it has reached as low a mint as convenient, attaching a new length to the electrode, connecting the holder to the up or end of the new length, and proceeding wlth the smelting process. A progressive feedin of the electrode into the furnace is thus 61- fectcd and the charge above the molten bathis maintained in as deep a layer as desired. When the mixture is properly proportioned, the operation is almost automatic, and the furnace needs no stoking and sim ily is kept full of the charge, and the meta and slag tapped when necessary.

Graphite pencils are preferably used, on account of their greater conductivity and the case with which they are machined, and care is taken that a good electrical and mechanical connection is assured in each joint. Preferably the lengths are united by screwjoints.

In the accompanying drawin s,-Figure 1 is a vertical section of a suita le electric furnace, showing the condition when the electrode has become as short as convenient and the holder has been removed from it preparatory to attaching a new length. Fig. 2 is a similar section thereof, 'showin the new length of electrode screwed on and attached to the holder ready to proceed with the smelting process.

In the drawings, A designates the body of the furnace, which, for the production of 'ferro-chrome, will usually be made of chrome ore; B is the lower electrode usually made of carbon; C is the lower electric terminal connecting with the bottom electrode; D is the layer of slag and molten char e, E is the layer of molten metal, .and is the granular or unfused charge which fills the furnace chamber.

G is the top of the furnace, which is preferably 'acketed in order that it me. be cooled y water circulation; H is an insulated water-cooled bushing surrounding the upper electrode.

I is the u er electrode commonl and dependently o erated by a switch so that PP 1 Y P preferably made in the form of a pencil of carbon or gra hite. This electrode is made in sections o'suitable length adapted for attachment to one another in such manner as to form a firm mechanical connection, and to afford suitable conductivity foncarrying the electric current. Preferably each section is formed with a screw-threaded projection a at one end, and a screw-threaded socket b at the other, so that successive sections may be screwed together, as clearly indicated in Fi 2. Each section also has preferably a be e 0 formed through it near its up er end through which to thrust a rod J, as s own in Fig. 1, to serve as a temporary en ort for the section and as a meansfor hol 'ng it while screwing on the next section.

K is the carbon holder connected by rods L with any suitable supporting head M which is hung from any suitable vertically adjustable support N. The particular construction of carbon holder is not essential but it is preferable that it shall be adapted to engage the screw-threaded pro ect1on a, and to this end it may advantageously be constructed in the manner set forth in the application of George 0. Seward for patent for carbon holders, filed May 3, 1904, Serial No. 206,250. r

In operation, whenever the proper electrode or carbon pencil I becomes so short that the carbon holder K a preaches inconveniently near to the top 0 the furnace, the smelting operation is suspended, a suitable rod J is thrust through the hole 0 in the pencil, and the carbon holder and pencil are iiisconnected. The holder lisi) than liftleg,

eavi the enci s11 orte y t e rm as sli d wn in Fig. L lhe holder is lifted high enough to enable another section of encil I to be applied as shown in Fig. 2.

his section is screwed on to the one below, and the holder is then screwed on to the top of this section; the rod J is then removed and the furnace is ready to resume the lsFmelting operation, being thus shown in %)ur invention is not limited to the construction of the electrode in sections which screw together, nor to the connection of the carbon holder by screwing it thereto. Any other suitable mode of connection of the sections to one another and to the carbon holder may be used. Nor is our invention limited to the use ofthe water-cooled top G or bushing H.

Thou h we have described with particularity the operation of our invention in a furnace having but one electrode, it is equally adapted to be used with furnaces containin two or more electrodes. When a multiphcity of encils is used in the same furnace, as is desirable with a owerful furnace, the circuit to each pencil may be inthecurrent may be cut off from the pencil under oing change and divided between the rest of the pencils, thus avoiding a reduction of the energ passing into the furnace or an interruption of the smelting operation. When con venient, the movable carbon holder may be replaced by a stationary form with whlch the encil maintains a sliding contact, which iias the advantage that new sections of pencil ma be attached as desired withoutbreaking t e flow of current through the electrode. l

The furnace shown in the drawing is what is commonly known as a single pole furnace, where the molten metal constitutes the other pole, but the invention is equally adapted to furnaces usin pencils of opposite polarity, though a sing e-pole furnace with either one or a plurality of dependin electrodes of the same )olarity is better adapted to the purposes of electric smelting as de-' scribed.

With a furnace of 1500 to 2000 horsepower, it is preferable that a plurality of electrodes be used, four eight'inch round pencils being very suitable, rather than one large electrode, for the reason that the gradual feeding down of the charge is greatly facilitated thereby.

Our invention, while it is applicable to the treatment of any refractory oxide or mixtures of oxids, or silicates, etc, is particularly adapted to the manufacture of ferrochromium, on account ofthe great refractoriness of the ore and its low conductivity at temperatures below its fusing point.

We are aware that it has been proposed to use horizontal sectional electrodes in an electric furnace wherein the electrodes enter an open space or chamber, and to apply new sections and feed the electrodes forward continuously as they are consumed; but such furnaces do not realize the object of our invention, since the electrodes are not buried in a mass of the ranular material, and the advantages of a buried are are not attained.

We claim as our invention 2- 1. The process of operating an electric furnace, which consists in maintaining a deep layer of the charge into which the electrode projects and by which it is surrounded, so that the are is buried beneath the charge, and effecting renewal of the electrode material by progressive feeding in of new lengths without withdrawal of the electrode from the charge.

2. The process of electric smelting, which consists in maintaining a deep layer of the charge above the molten bath and surrounding the lower part of an upright sectional electrode, so that the are is buried beneath the char e, fusing the charge by a current from sue electrode, and renewing the latter by successively attaching new sections thereof above the charge without withdrawing the electrodefrom the charge.

3..The process of'electric smelting in an electric furnace wherein an arc is maintained 5 between an upr' ht electrode and the molten bath beneath, w ich consists in maintaining a deep layer of the charge of granulated material above the molten bath and surrounding the lower part of the electrode, so that {'3 the arc is buried beneath the charge, gradually feeding the electrode downward as it is consumed, and renewing the electrode by successively attaching thereto new sections thereof above the charge and without withdrawing the electrode nor so lifting it as to 15 In witness whereof, we have hereunto si need our names 1n the presence of two SUbSCIl mg 20 witnesses.

GEORGE O. SEWARD.

FRANZ VON KUGELGEN. Witnesses J. H. WEBB,

F. voN BIDDER. 

